Which to buy first? D800 or 70-200mm f2.8

Hi, I currently have a D7000 and wanted to move up to FX camera but at the same time would like to get a new Lens unfortunately i can only afford one or the other at the moment so I was curious which to buy first. the D800 or 70-200mm f2.8? which would be a better investment currently? I been shooting weddings and portraits. Thanks in advance.